Human skin provides the body with a flexible barrier to the exterior environment through a highly integrated layered structure consisting of epidermis, dermis and subcutaneous tissues. Each layer has its own specific structure and functions. Mechanical behavior of the human skin is complex and well known to exhibit nonlinear and time-dependent mechanical behavior.
Soft biological tissues can be characterized by the state of tension, biomechanical and viscoelastic properties. Many attempts have been made to measure the biomechanical and viscoelastic properties of surfaces of soft biological tissues, for example human skin. The principal problem is how to evaluate human skin objectively, and to obtain numerical values, non-invasively, painlessly, quickly, and cost effectively, without causing the changes of the tissue being measured.
The US patent application US2011/0319792A1 describes a testing device for measuring biomechanical properties of skin for use by a surgeon, which has a force measurement device measuring the applied force, and a displacement measurement device measuring corresponding induced movement at a set of locations. The described testing device is not entirely satisfactory for the following reasons:                Long duration of measurement process, which may influence the numerical value of the measured parameter;        Only one parameter is measured, which is insufficient for objective characterization of the soft biological tissue;        The measurement process requires use of a flexible articulated arm which is a restricting factor as regards its ease of use, making the measurement process complicated and requiring long preparation;        The flexible articulated arm may allow measurements to be made only at certain angles of the measurement surface to the gravity vector;        The solution is difficult to use objectively in micro- or zero gravity, which is essential for manned space flight missions.        